Dust pickup systems for portable belt sanders



July 9, 1968 w, so 3,391,499

DUST PICKUP SYSTEMS FOR PORTABLE BELT SANDERS Filed March 17, 1966 2 SheetsSheet 1 l8 1:: I 111 1:15:1 I 1 o m Fig.2 i iii i 2 s, 3 5:: 1 E -muu|u| i 8 {H d T 3 l8 "a r "mi-.17. i s? L 1 1 INVEN TOR.

William A. Butson WITNESS: d/n'di Jofileeg/ l NEY July 9, 1968 w, Tso 3,391,499

DUS T PICKUP SYSTEMS FOR PORTABLE BELT SANDERS Filed March 17, 1966 2 Sheets-Sheet g INVENTOR. William A. Buison WITNESS.- lflw d/u'ob Jdleelgi AT 'O'RNEY United States Patent "ice 3,391,499 DUST PICKUP SYSTEMS FOR PORTABLE BELT SANDERS William A. Batson, Pickens, S.C., assignor to The Singer Company, New York, N.Y., a corporation of New Jersey Filed Mar. 17, 1966, Ser. No. 535,172 4 Claims. (Cl. 51-470) ABSTRACT OF THE DISCLQSURE A portable power operated belt sander has a timing belt drive between the motor drive shaft and one of the sanding drums. A rotary impeller is mounted on the drive shaft outboard of the timing belt drive which has a belt guard. A scroll housing for the impeller is mounted externally on the belt guard and has an unobstructed center intake aperture. Air flow conduit means is formed, in part, integrally with the belt guard but separately from the timing belt and, in part, as a detachable coupling element connected to the center intake aperture. Removal of the coupling element provides access for removal of the impeller and exposure of the timing belt for easy replacement thereof.

This invention relates to portable, power operated sanding machines of the endless abrasive belt type, and, more particularly, to dust pickup systems for removing the sanding dust resulting from their operation.

In the art of portable belt sanders it is common practice to drive the rear sanding-belt drum by a timing belt connected to a top-mounted electric motor having its shaft axis positioned transversely relative to the run of the sanding belt. In dust pickup systems for this type of sander, a problem arises in providing a dust-tight suction conduit between a pickup chamber located behind the rear sanding-belt drum and the inlet of an air pump driven by the top-mounted electric motor without adverse interference with the timing-belt drive.

Prior art solutions to this problem have, in general, resulted in noisy, inefficient and bulky systems.

It is therefore a principal object of the present invention to provide a new and improved dust pickup system for portable belt sanders of the type described wherein conduit means formed integrally with a belt guard combined with a removable series coupling member provide a direct and low impedance air flow path between a rearwardly located pickup chamber and the axial inlet opening of a centrifugal blower driven by the transverselymounted electric motor.

A further object of this invention is to provide a combined belt guard and dust conduit which may be factoryadapted as a common part to systems employing either built-in or external vacuum sources.

A still further object of this invention is to provide a centrifugal blower having a highly efficient center-intake impeller and a stationary scroll housing integrated with the belt-guard of a portable belt sander to create a pleasing appearance and at the same time improve the dustremoving efficiency of the system.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following detailed description of a specific embodiment when read in connection with the accompanying drawing, in which:

FIG. 1 is a side elevation view, partly broken away, of a portable belt sander provided with a preferred em- 3,391,499 Patented July 9, 1968 bodiment of the dust pickup system ,of the present invention,

FIG. 2 is a top plan view of the device of FIG. 1, partly in section taken substantially on line 2-2 of FIG. 1.

FIG. 3 is a disassembled perspective view showing essential parts of the system of this invention.

Referring now in greater detail to the illustrated embodiment, the portable belt sander comprises a main frame 10 including a side wall 11, an end wall 12 and an upper wall 13. Rising from the upper wall 13 and integral with the frame 10 is a cylindrical motor housing 14- within which is mounted an electric driving motor 15 having a shaft 16 extending from one end thereof transversely of the frame 10.

The frame 10 supports a pair of revolvable drums or pulleys 17 and 18 located adjacent the longitudinal ends thereof and an endless flexible sanding belt 19 is trained over the drums. The forward drum 17 is the idler drum, while the rearward drum 18 is the driving drum and is operatively connected to and driven by the electric motor 15.

The motor shaft 16 carries a toothed pulley 2(1 and a stub shaft 21 carries a toothed pulley 22 drivingly connected to pulley 20 by means of a timing belt 23. The stub shaft 21 carries a pinion (not shown) which meshes with and drives a gear 24 fixed for rotation with the driving drum 18. It will be seen from FIG. 1 that clockwise rotation of shaft 16 results in counterclockwise rotation of the drum 18 thereby moving the lower ply of the belt 19 rearwardly along the base of the housing 10. A sole plate 25 provides a backing support for the belt 19 as the abrasive surface thereof is pressed against the surface of the workpiece.

A handle 27 cast integrally with the motor housing 14 provides forward and aft grip portions 29 and 28 for convenient manipulation of the tool. A switch having trigger 30 is mounted in the handle and an electrically conducting cable 31 extends from the rear .of the handle for connection to a conventional source of electrical power.

Thus far there has been described a portable belt sander of a general prior art type described in greater detail in United States Patent No. 2,774,198 to which reference may be had for a more complete understanding thereof.

There will now be described a dust pickup system for this sander in accordance with the present invention.

A cover element 32 forming a combination belt guard and suction conduit, shown in detail in FIG. 3, preferably made of moldable insulating material is formed with two separate internal compartments 33 and 34 and is removably secured to the frame 10 by means of screws 3535- which pass through apertured bosses 36-36 and are threaded into portions of the side wall 11.

The compartment 33 houses and guards the timing belt 23 and communicates with the atmosphere through a series of ventilating apertures 37 at the top end and a single slotted portion 38 at the bottom end thereof.

The compartment 34 forms a suction conduit and communicates at one end with a dust chamber 39 located behind the rear sanding drum 18. This dust chamber 39 is an integral part of the main frame 10 and runs parallel with the drum 18 for its entire length. The outer wall 12 of the dust chamber 39 extends vertically downwardly very close to the work surface, whereas an inner Wall 40 next to the drum 18 does not extend downwardly as far and this permits dust to be more easily drawn into the chamber 39 from the drum 18.

The suction conduit 34 leads along the top edge of the compartment 33 and terminates approximately midway along said edge in an apcrtured boss 41 which projects perpendicularly with respect to the outer surface of the cover 32.

The suction conduit 34 is sealed dust tight by means of a molded filler plate 4-2 held entrapped between the cover 32 and the main frame by one of the screws 3535. The lower end of the conduit 34 is formed with a rabbeted edge 43 which fits within a shouldered portion 44 of frame 19 and provides a dust-tight seal with respect to the dust chamber 39 as seen best in FIG. 3.

In one form of the invention as seen in FIG. 3 a flexible hose 60 may be coupled to the apertured boss 41 and the opposite end of the hose may be attached to a commercial or a domestic vacuum cleaner for dust removal. When the above dust pickup system is not used, a cap 61 snaps in place over the boss 41.

An aperture 45 located centrally in the upper end of the cover 32 and used for a purpose to be described presently is, in the first form of this invention, permanently sealed With a cap 62 of a form similar to the cap for the boss 41 described above.

When it is desired to manufacture a complete integral self-contained dust pickup system which is not dependent on any external vacuum sources, the same identical parts as described above are used with the following exceptions and additional parts:

The rotor assembly for the built-in dust pickup system has a longer shaft 16 which extends outwardly through the aperture 45 so that a blower impeller 46 can be mounted thereon outboard of the toothed pulley 26 and externally of the cover 32, as shown best in FIG. 2. A molded plastic scroll housing 47 for the impeller 46 is secured by cementing to the cover element 32 and provides a blower casing having a large center inlet 48 for impeller 46. Dust is exhausted through an outlet duct 53 formed integrally with the scroll housing 47 and is collected in a removable cloth bag 54 attached to duct 53 as seen best in FIG. 1. This type of blower structure is most efiicicnt and sufiicient capacity can be obtained with a small-diameter impeller which greatly reduces the noise generated as compared with the usual larger-diameter impellers made necessary by the annular type of inlet opening required by the usual inboard mounting of the impeller 46.

A coupling element 49 made from molded plastic material fits over the apertured boss 41 and is formed with a resilient annular lip portion 5% which provides a snap-in securement with respect to the center inlet 48 as shown in FIG. 2. The removable coupling element 49 thus completes a dust-tight suction conduit defining a low impedance path for air flow from the dust pickup chamber 39 to the axial center inlet 48 which avoids awkward interference with the timing belt 23 and results in a pleasing wellbalanced appearance and with no compromise with respect to the dust-removing capability of the system.

The removable coupling 49 also provides easy access means for replacement of the timing belt 23 as follows:

The center inlet aperture 48 is large enough to permit entry there-through of the impeller 46 which is assembled to shaft 16 (subsequently to securement of cover 32) by means of a cap screw 51 threaded into the end thereof to hold the impeller hub 52 in driving relation with the pulley 20. Removal of coupling 49 thus provides access through aperture 48 to screw 51 for its removal and that of the impeller 46 whereupon the entire cover element 32 may be removed by removal of screws 3535 to fully expose the timing belt 23 and pulleys and 22.

It will be seen that the use of a removable coupling 49 as part of the suction conduit path integrated with the belt-guard in accordance with this invention results in ing dust pickup systems either (a) for usewith built-in or (b) for use with external vacuum sources. In the field of highly-competitive, mass-produced portable electric tools, this simplified assembly is of the utmost importance in minimizing production costs.

Having thus set forth the nature of the invention, what is claimed herein is:

1. In combination with a portable power operated sander of the type having a frame; a pair of longitudinally spaced laterally extending drums rotatably mounted on the frame and supporting an endless sanding belt thereon; a motor mounted on the frame having a laterally extending drive shaft; a driving connection between the motor and one of the drums including a drive pulley mounted on the drive shaft; a driven pulley drivingly connected to said drum and an endless driving belt mounted on the drive and driven pulleys; a guard for said driving belt removably secured to the exterior of the frame; a dust pickup system comprising a pump having a rotary impeller mounted on the drive shaft outboard of the drive pulley; a scroll housing for the impeller mounted on the belt guard and formed with a center intake aperture; means providing a dust pickup chamber adjacent one of tie drums; conduit means formed, in part, integrally with said belt guard and, in part, separably from said belt guard for connecting the pickup chamber with the center intake aperture.

2. Apparatus according to claim 1 in which that part of the conduit means formed integrally with the belt guard is located entirely externally of the driving belt and terminates at one end in an external apertured boss located adjacent to the center intake aperture.

3. Apparatus according to claim 2 in which that part of the conduit means formed separably from the belt guard is a detachable coupling element providing a passage for air flow between the external apertured boss and the center intake aperture.

4. A portable electric belt sander comprising a frame; a pair of longitudinally spaced laterally extending drums rotatably mounted on the frame for supporting an endless sanding belt thereon; an electric motor mounted on the frame having a drive shaft extending exteriorly of the frame; a timing belt drivingly connecting the drive shaft with one of the drums; a dust pickup chamber located adjacent said one of said drums; a belt guard removably secured to the exterior of said frame and forming therewith a housing for the timing belt; a pump having a rotary impeller mounted on the drive shaft exteriorly of the belt guard, a scroll housing secured to the belt guard and defining an impeller-receiving chamber and for-med with a center intake aperture of a diameter larger than said impeller; means formed on said belt guard providing a suction conduit communicating at one end with the dust pickup chamber and terminating at the opposite end in an external apertured boss; and detachable coupling means forming, when in place, a passage for air fiow between the apertured boss and the center intake aperture and, when removed, providing access for removal of said impeller through said intake aperture.

References Cited UNITED STATES PATENTS 2,654,190 10 /1953 Mitchell 51--17O 2,774,198 12/1956 Emmons 51170 3,049,842 8 1962 Murschel 51170 3,180,063 4/1965 Burrows et al. 51-170 LESTER M. SWINGLE, Prinmry Examiner. 

